GB1132510A - Flow regulating valve mechanism - Google Patents

Abstract

1,132,510. Motor vehicles. NEW YORK AIR BRAKE CO. 31 Oct., 1966 [21 Feb., 1966], No. 48695/66. Heading B7H. [Also in Division F2] An hydraulic circuit in a motor vehicle for operating an implement and power steering comprises three pumps, P 1 , P 2 , P 3 , drawing fluid from a reservoir 15 and driven by an engine 14, the output from P 3 being delivered directly to the implement circuit 13 through a line 18 and the output from P 1 being delivered to a valve device 11 through which it passes via an input 22, shuttle valve 27 and line 17 to a steering circuit 12. The output from P 2 passes through a line 19 and into the valve device 11, where, below a predetermined engine speed, it flows past a valve spool 35 and through channels 38, 24a and through radial orifices 29 in the shuttle valve 27 to supplement the flow from P 1 in the steering circuit. The shuttle valve 27 is biased to the left by a spring 31 and has an axial bore from which extend the orifices 29 and a replaceable pair of flow restricting orifices O 1 and O 2 . The valve spool 35 is biased to the left by a spring 42 and has internal passages 46, 47 for transmitting fluid pressure to its left face 45, its right face 33 being subjected to the pressure in passage 26 downstream of the valve 27 through a passage 49. The line 19 from P 2 enters the valve device 11 at a chamber 24 from which channels 39 and 24b extend in parallel with channels 38, 24a, channel 24b leading through a chamber 25, closed by a check valve 51 to a line 21 connected to the implement supply line. Up to a certain speed of the engine, P 1 and P 2 jointly supply the steering circuit and P 3 the implement circuit. Beyond a certain pressure gradient across the orifice O 1 , the pressure in channel 24a acting through passages 46 and 47 causes valve spool 35 to move so that an orifice 03 begins to close while an orifice O 4 opens, allowing fluid to enter channel 24b. Over a certain range of speed, the combined outputs from P 1 and P 2 to the steering circuit remain constant while part of the P 2 output is added to the P 3 output in the implement circuit. At a further predetermined speed, the pressure build-up on the face 27a of shuttle valve 27 causes it to move to the right against the pressure of spring 31, to a position beyond the channel 24a. The pressure gradients across O 2 and O 1 now act in series so that the relative pressures on the faces 45 and 33 of valve spool 35 causes the orifice O 3 to be closed so that the total outputs from P 2 and P 3 are directed to the implement circuit while the steering circuit is supplied solely by P 1 . The variable parameters determining the various speeds are the orifices O 1 and O 2 and the springs 31 and 42. There may be a slight initial drop of pressure in the steering circuit at engine speeds above that at which the orifice O 3 closes.